Optical hard coating polymer films are becoming increasingly important in the display industry. New applications are being developed for hard coating films applied to optical display devices in, for example, the computer, television, appliance, mobile phone, aerospace and automotive industries.
The hard coatings are applied to the optical display surfaces to protect them from scratching and marking. Desirable product features in optical hard coats are the combination of a low percentage of reflected light (e.g. 1.5% or lower), durability to scratches and abrasions, and resistance to inks and stains.
Materials that have been used to date for surface protection include fluorinated polymers, or fluoropolymers. Fluoropolymers provide advantages over conventional hydrocarbon based materials in terms of high chemical inertness (in terms of acid and base resistance), dirt and stain resistance (due to low surface energy), low moisture absorption, and resistance to weather and solar conditions.
Because of the low surface energy characteristic that prevents satisfactory adhesion, and inherent softness that prevents good mechanical durability, the use of fluoropolymer coatings alone is not preferred. Thus, fluoropolymers have been investigated that are crosslinked to a hydrocarbon-based hard coating formulation that improves hardness and interfacial adhesion to a substrate. For example, it is known that free-radically curable perfluoropolyethers provide good repellency to inks from pens and permanent markers when added to ceramer hard coat compositions, which comprise a plurality of colloidal inorganic oxide particles and a free-radically curable binder precursor, such as described in U.S. Pat. No. 6,238,798 to Kang. However, the perfluoropolyether derivatives are not sufficiently compatible with ceramer hardcoats and tend to cause the coatings to dewet and produce a rough surface.
Thus, it is desirable to form a fluoropolymer-based hard coating with satisfactory smoothness, durability, ink and stain repellency and which also has good optical qualities.